阅读说明：本技术 一种控制涡轮叶片晶粒度的方法 (Method for controlling grain size of turbine blade ) 是由 任维鹏 于 2020-05-13 设计创作，主要内容包括：本发明是一种涡轮叶片晶粒度的控制方法,所述涡轮叶片是采用熔模精密铸造工艺加工,其特征在于：该方法是在型壳的制备过程中,将涡轮叶片的蜡模模组中榫头和其它需在铸造过程中细化晶粒的部位浸入作为面层浆料的细化剂浆料,使浸入部分与细化剂浆料充分接触；所述细化剂浆料的配制是在1升硅溶胶中,加入3～6公斤的白刚玉粉和0.5～3公斤的铝酸钴。本发明解决了一般工艺条件下等轴晶涡轮叶片铸造中叶片叶身与厚大榫头部位晶粒度难以兼顾的难题,获得的榫头表面细晶、叶身粗晶的涡轮叶片,其榫头疲劳性能优良,同时叶身具有较好的高温强度,保证了叶片使用可靠性。(The invention relates to a method for controlling the grain size of a turbine blade, wherein the turbine blade is processed by adopting an investment precision casting process, and is characterized in that: in the method, in the preparation process of a shell, a tenon in a wax mold module of a turbine blade and other parts needing grain refinement in the casting process are immersed into refiner slurry serving as surface layer slurry, so that the immersed part is fully contacted with the refiner slurry; the refiner slurry is prepared by adding 3-6 kg of white corundum powder and 0.5-3 kg of cobalt aluminate into 1 liter of silica sol. The invention solves the problem that the grain sizes of the blade body and the thick and large tenon part are difficult to be considered in the casting of the equiaxial crystal turbine blade under the general process condition, and the obtained turbine blade with the fine-grain tenon surface and the coarse-grain blade body has excellent tenon fatigue performance, and simultaneously the blade body has better high-temperature strength, thereby ensuring the use reliability of the blade.)

1. A method for controlling the grain size of a turbine blade, wherein the turbine blade is processed by adopting an investment precision casting process, and is characterized in that: in the method, in the preparation process of a shell, a tenon in a wax mold module of a turbine blade and other parts needing grain refinement in the casting process are immersed into refiner slurry serving as surface layer slurry, so that the immersed part is fully contacted with the refiner slurry;

the refiner slurry is prepared by adding 3-6 kg of white corundum powder and 0.5-3 kg of cobalt aluminate into 1 liter of silica sol.

2. The method of controlling the grain size of a turbine blade of claim 1, wherein: after the wax pattern module of the turbine blade finishes the dipping of the refiner slurry, uniformly sanding the surface of the wax pattern module of the turbine blade through a sanding machine, drying, removing residual sand grains, immersing the rest exposed wax parts of the wax pattern module of the turbine blade into common surface layer slurry without the refiner, fully contacting the immersed parts with the common surface layer slurry, taking out the wax pattern module of the turbine blade, uniformly sanding the surface of the wax pattern module of the turbine blade through the sanding machine, and drying;

the preparation of the common surface layer slurry is to add 3-6 kg of white corundum powder into 1L of silica sol.

3. The method of controlling the grain size of a turbine blade of claim 1, wherein: before the wax pattern module of the turbine blade is soaked with the refiner slurry, the part of the wax pattern module of the turbine blade, which does not need to refine grains in the casting process, is soaked into the common surface layer slurry serving as the surface layer slurry, so that the soaked part is fully contacted with the common surface layer slurry, the wax pattern module of the turbine blade is taken out, sand is uniformly sprayed to the surface of the wax pattern module of the turbine blade through a sand sprayer, the turbine blade is dried, and after residual sand grains are removed, the refiner slurry is soaked;

the preparation of the common surface layer slurry is to add 3-6 kg of white corundum powder into 1L of silica sol.

4. The method of controlling the grain size of a turbine blade of claim 1, 2 or 3, wherein: and immersing the wax pattern module subjected to surface layer slurry impregnation into the back layer slurry, fully contacting the surface of the wax pattern module with the slurry, taking out the wax pattern module, uniformly sanding the surface of the wax pattern module through a sanding machine, and drying.

5. The method of controlling the grain size of a turbine blade of claim 4, wherein: the back layer slurry is prepared by adding 2-5 kg of mullite powder into 1 liter of silica sol.

6. The method of controlling the grain size of a turbine blade of claim 1, 2 or 3, wherein: when different surface layer sizing agents are soaked, an overlapping coverage area with the width of more than 5mm is ensured at the joint.

7. The method of controlling the grain size of a turbine blade of claim 1, wherein: the shell heating temperature in the precision investment casting is 950-1050 ℃.

8. The method of controlling the grain size of a turbine blade of claim 1, wherein: the method comprises the following steps:

firstly, preparing a wax mould module of the turbine blade, and turning to a shell preparation process;

step two, soaking tenons of the wax mold modules of the turbine blades and other parts needing grain refinement in the casting process into refiner slurry serving as surface layer slurry, enabling the soaked parts to be fully contacted with the refiner slurry, taking out the wax mold modules of the turbine blades, uniformly sanding the surfaces of the wax mold modules of the turbine blades through a sanding machine, and drying;

the preparation of the refiner slurry is to add 3-6 kg of white corundum powder and 0.5-3 kg of cobalt aluminate into 1 liter of silica sol;

step three, removing residual sand grains on the surface of the wax pattern module of the turbine blade treated in the step two, particularly carefully cleaning the exposed wax part, immersing the wax pattern module of the turbine blade cleaned completely into common surface layer slurry without a refiner, fully contacting the immersed part with the common surface layer slurry, taking out the wax pattern module of the turbine blade, uniformly sanding the surface of the wax pattern module of the turbine blade through a sanding machine, drying, removing the residual sand grains, and then dipping the refiner slurry;

the preparation of the common surface layer slurry is to add 3-6 kg of white corundum powder into 1L of silica sol;

step four, immersing the wax pattern module of the turbine blade processed in the step three into the back layer slurry to enable the surface of the wax pattern module of the turbine blade to be fully contacted with the back layer slurry, taking out the wax pattern module of the turbine blade, uniformly sanding the surface of the wax pattern module of the turbine blade through a sanding machine, and drying;

the preparation of the back layer slurry is to add 2-5 kg of mullite powder into 1 liter of silica sol;

step five, the wax mold module of the turbine blade processed in the step four is continuously prepared according to the step four to the required shell layer number;

dewaxing and roasting to obtain a casting shell;

and step seven, heating the shell obtained in the step six to 950-1050 ℃ and then pouring.

Technical Field

The invention discloses a method for controlling the grain size of a turbine blade, and relates to the technical field of investment precision casting.

Background

Turbine blades for aircraft engines and gas turbines are subject to high temperatures, centrifugal forces, vibrations, thermal fatigue, etc. during operation, and therefore the blades need to have high strength, sufficient plasticity and impact toughness, good oxidation resistance, thermal fatigue properties and structural stability, and the turbine blades are generally made of high temperature alloys. Low pressure turbine blades operating at medium and low temperatures and some high pressure turbine blades operating at medium and high temperatures are typically cast using equiaxed grain.

The grain size has a great influence on the mechanical properties of the alloy. Under the condition of medium and high temperature, the grain boundary diffusion can be obviously accelerated to become a weak link, so that the alloy strength is reduced, and therefore, the high-temperature performance of the alloy can be improved by large-size grains. At low temperatures, however, the smaller size of the grains improves certain mechanical properties, such as fatigue properties.

Typically, the blade body is subjected to a relatively high temperature environment, coarse grains are beneficial for performance, the bucket dovetail operates at a temperature well below that of the blade body, and it is substantially fatigue loaded, with a fine grain structure being desired.

Under the production conditions of a common investment casting process, the crystal grains of the blade casting are generally coarse, and when a specific process is adopted for casting, a fine crystal grain structure can be obtained. Low pressure turbine blades operating at medium to low temperatures typically use surface fine grain casting techniques in order to achieve good fatigue performance and reliability. For high-pressure turbine blades working under medium-high temperature conditions, if isometric crystal casting is adopted, a surface fine crystal process is not generally adopted, and the blade body is controlled to be a coarse crystal structure so as to ensure high-temperature strength.

For isometric crystal casting high-pressure turbine blades working under medium-high temperature conditions, under the same casting conditions, crystal grains at the tenon part with larger thickness are obviously increased relative to the blade body with thin wall, and the performance of the tenon of the blade connected with a turbine disc and positioned in a medium-low temperature region is unfavorable. Therefore, a specific process is required to be adopted for treatment, the blade body is controlled to be coarse-grained, and the abnormally increased grains of the tenon are avoided, so that the fatigue performance of the tenon is avoided being reduced while the high-temperature strength of the blade body is ensured, the service reliability of the blade is ensured, and the service life of the blade is prolonged.

Disclosure of Invention

The invention provides a method for controlling the grain size of a turbine blade, aiming at obtaining an equiaxial crystal casting turbine blade with a blade body and a tenon respectively having proper grain size grades by a simple, feasible and low-cost process method.

In order to achieve the purpose, the technical scheme of the invention comprises the following steps:

in the method for controlling the grain size of the turbine blade, the turbine blade is processed by adopting an investment precision casting process, and the method is characterized in that: in the method, in the preparation process of a shell, a tenon in a wax mold module of a turbine blade and other parts needing grain refinement in the casting process are immersed into refiner slurry serving as surface layer slurry, so that the immersed part is fully contacted with the refiner slurry;

the refiner slurry is prepared by adding 3-6 kg of white corundum powder and 0.5-3 kg of cobalt aluminate into 1 liter of silica sol.

In one implementation, after the wax mold module of the turbine blade finishes dipping of the refiner slurry, uniformly sanding the surface of the wax mold module of the turbine blade through a sanding machine, drying, removing residual sand grains, immersing the rest exposed wax parts of the wax mold module of the turbine blade into common surface layer slurry without the refiner, enabling the immersed parts to be fully contacted with the common surface layer slurry, taking out the wax mold module of the turbine blade, uniformly sanding the surface of the wax mold module of the turbine blade through the sanding machine, and drying;

the preparation of the common surface layer slurry is to add 3-6 kg of white corundum powder into 1L of silica sol.

In one implementation, before the wax pattern module of the turbine blade is soaked with the refiner slurry, the part, which does not need to refine grains in the casting process, of the wax pattern module of the turbine blade is soaked into the ordinary surface layer slurry serving as the surface layer slurry, the soaked part is fully contacted with the ordinary surface layer slurry, the wax pattern module of the turbine blade is taken out, sand is uniformly sprayed to the surface of the wax pattern module of the turbine blade through a sand sprayer, the turbine blade is dried, and after residual sand grains are removed, the refiner slurry is soaked;

the preparation of the common surface layer slurry is to add 3-6 kg of white corundum powder into 1L of silica sol.

In one implementation, the wax pattern module which is impregnated with the surface layer slurry is immersed into the back layer slurry, so that the surface of the wax pattern module is fully contacted with the slurry, the wax pattern module is taken out, and the surface of the wax pattern module is uniformly sanded by the sanding machine and is dried.

In one embodiment, the back layer slurry is prepared by adding 2-5 kg of mullite powder to 1L of silica sol.

In one implementation, different facer slurries, when impregnated, ensure an overlapping coverage area of 5mm or more in width at the interface.

In one implementation, the shell heating temperature in the investment precision casting is 950-1050 ℃.

In one implementation, the steps of the method are as follows:

firstly, preparing a wax mould module of the turbine blade, and turning to a shell preparation process;

step two, soaking tenons of the wax mold modules of the turbine blades and other parts needing grain refinement in the casting process into refiner slurry serving as surface layer slurry, enabling the soaked parts to be fully contacted with the refiner slurry, taking out the wax mold modules of the turbine blades, uniformly sanding the surfaces of the wax mold modules of the turbine blades through a sanding machine, and drying;

the preparation of the refiner slurry is to add 3-6 kg of white corundum powder and 0.5-3 kg of cobalt aluminate into 1 liter of silica sol;

step three, removing residual sand grains on the surface of the wax pattern module of the turbine blade treated in the step two, particularly carefully cleaning the exposed wax part, immersing the wax pattern module of the turbine blade cleaned completely into common surface layer slurry without a refiner, fully contacting the immersed part with the common surface layer slurry, taking out the wax pattern module of the turbine blade, uniformly sanding the surface of the wax pattern module of the turbine blade through a sanding machine, drying, removing the residual sand grains, and then dipping the refiner slurry;

the preparation of the common surface layer slurry is to add 3-6 kg of white corundum powder into 1L of silica sol;

step four, immersing the wax pattern module of the turbine blade processed in the step three into the back layer slurry to enable the surface of the wax pattern module of the turbine blade to be fully contacted with the back layer slurry, taking out the wax pattern module of the turbine blade, uniformly sanding the surface of the wax pattern module of the turbine blade through a sanding machine, and drying;

the preparation of the back layer slurry is to add 2-5 kg of mullite powder into 1 liter of silica sol;

step five, the wax mold module of the turbine blade processed in the step four is continuously prepared according to the step four to the required shell layer number;

dewaxing and roasting to obtain a casting shell;

and step seven, heating the shell obtained in the step six to 950-1050 ℃ and then pouring.

The invention has the following advantages and beneficial effects:

the invention provides a method for controlling the grain size of a turbine blade, which has simple operation steps and is mainly characterized in that the grain size control of the blade with coarse grains on a blade body and fine grains on the surface of a tenon is realized by adopting a coating process of refiner slurry in a shell preparation stage and matching with smelting and pouring. The cobalt aluminate refiner particles in the refiner slurry are non-uniformly nucleated substrates, promoting the increase of the number of nucleation, thereby obtaining a fine crystalline structure. In addition, in the method, the preparation of the shell surface layer is finished in two times, and the method can be implemented by firstly coating refiner slurry on the tenon of the blade, sanding and drying, cleaning residual sand grains, then coating the surface layer slurry without the refiner on the blade body part, sanding and drying. The surface refiner of the tenon part can ensure that the grain size of the tenon surface of the blade after pouring is less than 2 grades, and the grain size of the blade body part without the refiner is more than 3 grades.

The invention solves the problem that the grain sizes of the blade body and the thick and large tenon part are difficult to be considered in the casting of the equiaxial crystal turbine blade under the general process condition, and the obtained turbine blade with the fine-grain tenon surface and the coarse-grain blade body has excellent tenon fatigue performance, and simultaneously the blade body has better high-temperature strength, thereby ensuring the use reliability of the blade.

Drawings

FIG. 1 is a schematic view of a wax pattern die set wax pattern surface coating area of a turbine blade according to the present invention, wherein the fine-grained region is a region coated with a refiner paste, 1, blade body; 2. a tenon; 3. a pouring channel; 4. a pouring cup.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.